@liaizon Oxford Political Review has a Mastodon account; and it's technically a part of Oxford University, a school that goes back at least to 1096 (earliest factual evidence) if not earlier. The publication itself, however, only dates back to 2018, so I'm not sure if this counts.

https://mastodon.social/@oxfordpolrev

@liaizon I think the best candidate would be some Roman Catholic diocesis. Regarding German dioceses, there is an account for @bistumtrier, which dates back to Roman antiquity, although I cannot decide whether it is an official account. @bistumpassau, @bistumwuerzburg, @BistumAugsburg were all founded the 8th century. There might me many accounts for very old dioceses in other countries as well.

Roman Catholic Diocese of Trier dates back to 250AD ( @bistumtrier)

The Roman Catholic Diocese of Würzburg was founded in 741 or early 742AD ( @bistumwuerzburg)

The Roman Catholic Diocese of Augsburg dates back to possibly the 11th century but seems the exact date is uncertain ( @BistumAugsburg)

Thanks for discovering these accounts @steffenloewe!